This invention relates to a disc memory device such as a magnetic disc storage.
In a movable head type magnetic disc storage used as a memory device, a magnetic head is positioned at a desired track on the surface of a magnetic disc through servo control. In positioning, as soon as a request for calling a specified piece of information on the magnetic disc surface has been issued, the magnetic head is moved at a high speed radially of the magnetic disc so as to decrease the call time. Accordingly, an actuator of relatively high mechanical output energy is used for moving the magnetic head and for positioning.
Accordingly, when the high output actuator which is fixedly mounted on a base is energized for quick movement of the magnetic head in response to a call instruction, it is affected by abrupt acceleration/deceleration control to undergo a shock, and consequently a carriage carrying the magnetic head and the base are forced to vibrate, followed by occurrence of off tracking (or a tracking error) in the magnetic disc memory device.
With the trend toward increased recording density, the above disadvantage has been more aggravated. A prior art technique for coping with this problem is found in a proposal disclosed in, for example, U.S. Pat. No. 3,643,242 wherein a magnetic circuit block for a voice coil motor serving as an actuator is made in the form of a movable structure which can absorb the above-mentioned shock. Disadvantageously, the movable structure is massive and a device of this proposal becomes large-sized and complicated by incorporating the massive movable structure. In addition, the dust generated from the movable structure can not be shielded sufficiently.